What Velocity Does the Boy Gain After Throwing the Jug?

  • Thread starter Thread starter GodAllen
  • Start date Start date
  • Tags Tags
    Momentum Roller
Click For Summary

Homework Help Overview

The problem involves a boy on roller blades who throws a jug of water, and the objective is to determine the velocity gained by the boy after the throw. The context is rooted in the principles of conservation of momentum.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the conservation of momentum, noting that the total momentum before the throw is zero. There are attempts to set up equations based on momentum before and after the throw, and some participants express uncertainty about the initial conditions and the application of formulas.

Discussion Status

Some guidance has been offered regarding the conservation of momentum, with participants attempting to outline the equations involved. However, there is a lack of explicit consensus on the final interpretation of the results, and some participants question the completeness of the provided reasoning.

Contextual Notes

There are indications that the discussion is constrained by the forum's rules against providing complete solutions, which has led to some reiteration of the problem setup and the need for clarity in the approach taken.

GodAllen
Messages
3
Reaction score
0

Homework Statement



A boy on roller blades throws a jug of water away from himself, giving it a speed of 14m/s. The boy's mass is 38kg and the mass of he jug and the water is 7.9kg. What is the velocity gained by the lad?


Homework Equations


Not sure.

The Attempt at a Solution


Not sure.
 
Physics news on Phys.org
This is a simple conservation of momentum problem, so assume that at the beginning, total momentum is equal to 0
Afterwards, the total momentum must stay the same.
Thus:
Momentum(before) = Momentum(boy) + Momentum(jug)
This should be enough to get you started
 
so you apply the formula P(before)=P(after). (And by the way the momentum before is 0 as the intial velocities of the boy and the jug are 0 as P(before)= m(boy)xv(boyintial)+m(jug)xv(jug int.))Hope u understood until now.
p(after)=m(boy)xv(boy final)+m(jug)xv(jug)
P(after)=38kg(v)+7.9kg(14m/s)
P(after)=38v+110.6
P(before)=p(after)
0=38v+110.6
38v=-110.6
V=-2.9
So velocity of the boy is 2.9 and its direction is in the opposite direction that he threw the jug in.
Thanks for reading in my answer and i hope u understand and everbody as well since i am a new user.
 
Last edited:
mido808 said:
so you apply the formula P(before)=P(after). (And by the way the momentum before is 0 as the intial velocities of the boy and the jug are 0 as P(before)= m(boy)xv(boyintial)+m(jug)xv(jug int.))Hope u understood until now.
p(after)=m(boy)xv(boy final)+m(jug)xv(jug)
P(after)=38kg(v)+7.9kg(14m/s)
P(after)=38v+110.6
P(before)=p(after)
0=38v+110.6
38v=-110.6
V=-2.9
So velocity of the boy is 2.9 and its direction is in the opposite direction that he threw the jug in.
Thanks for reading in my answer and i hope u understand and everbody as well since i am a new user.
you are not supposed to solve the whole problem. this is against pf rules
https://www.physicsforums.com/showthread.php?t=414380
 

Similar threads

Replies
11
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 13 ·
Replies
13
Views
1K
Replies
2
Views
3K
  • · Replies 1 ·
Replies
1
Views
56K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K
Replies
3
Views
2K